The present invention relates to a liquid filter/heat exchanger unit, in particular for motor vehicles, comprising a liquid filter with a filter element in a filter housing, a heat exchanger with a liquid inlet and outlet, the unfiltered liquid side of the filter element communicating with the heat exchanger outlet; a bypass which bypasses the heat exchanger and connects the heat exchanger inlet directly to the unfiltered liquid side of the filter element, and a switching element for controlling liquid flow into the heat exchanger and/or the bypass.
To cool the oil in internal combustion engines, a liquid filter/heat exchanger unit is flange-mounted on the engine block, so that the oil required for lubricating the engine can be cleaned and cooled. The liquid filter/heat exchanger unit comprises a liquid filter having a filter element situated in a filter housing and a heat exchanger connected to the filter housing. The entire unit is flange-mounted on the engine block, so that the unfiltered, hot raw oil from the engine block first goes through an inlet in the liquid filter/heat exchanger unit into the heat exchanger, where it is cooled and then is passed to the unfiltered oil side of the filter element and is cleaned in the filter element. The cooled and cleaned oil from the clean side of the filter element then is reintroduced into the oil circuit in the engine block.
In a cold start, particularly at very cold temperatures, in order to prevent the dirty oil entering the heat exchanger from clogging it due to its increased viscosity at low temperatures and thus interfering with steady-state flow through the heat exchanger, a bypass branches off from the heat exchanger inlet directly to the unfiltered side of the filter element. In this bypass there is a bypass valve, which is in the closed position at the regular operating temperature and thus obstructs the bypass but opens at low temperatures, so that the dirty oil bypasses the heat exchanger and is sent directly to the unfiltered side of the filter element.
The switching function of the bypass valve is usually controlled based on the pressure in the inlet, which increases when there is blockage of the oil in the heat exchanger. If the pressure exceeds an allowed limit value, the bypass valve is opened and the dirty oil can flow directly to the unfiltered side of the filter element. This prevents clogging of the heat exchanger and also facilitates faster heating of the oil.